Patent GB-815214-A (GB)
Title: Cyclic batch process for the production of esters
Inventor: HOLLAND STEPHEN DONALD
IPC: C07C69/00
Filed: 1957-09-25
Abstract: Esters are prepared by (1) boiling a molar excess of an alcohol with a carboxylic acid in the presence of an esterification catalyst, which has a higher boiling point than the ester being produced, and also in the presence of a waterentrainer which distils off and continuously removes from the system the water produced in the reaction; (2) distilling from the reaction mixture firstly excess alcohol and entrainer, and secondly the ester, to leave a residue which includes the catalyst; (3) adding to this residue the alcohol and entrainer recovered in step 2 and further quantities of the alcohol, carboxylic acid and catalyst to result in a mixture containing a molar excess of the alcohol; (4) heating this mixture to distil off esterificationwater; and repeating step 2.  Steps 2, 3 and 4 may be repeated until the residue containing catalyst is unsuitable for further use.  The process is particularly applicable to the production of the acetates of the ethylene glycol monoalkyl ethers, and of di-ethylene glycol monoethyl ether.  Suitable catalysts are: sulphuric acid, ethyl sulphuric acid, ethane sulphonic acid, benzene sulphonic acid, p-toluene sulphonic acid, oxalic acid, succinic acid, tartaric acid, acetic acid, and dichloroacetic acid.  Suitable entrainers are: ethylene dichloride, propylene dichloride, toluene and benzene.  In an example, a mixture of glacial acetic acid (1 mole.), ethylene glycol monoethyl ether (1.2 moles.), toluene (15 per cent by volume), and p-toluene sulphonic acid (0.3 per cent by weight) is heated to boiling in a vessel fitted with a distillation column which is operated at total reflux for 15 minutes.  Water is then removed via a separator at the top of the column.  A mixture of glycol ether and toluene (fraction B) is then removed at a headtemperature of 102-120 DEG  C. using a reflux ratio of 7 : 1. Heating under reflux is then continued to cause any remaining traces of acetic acid to react; after which the remainder of fraction B is distilled off until the headtemperature reaches 154 DEG  C.  At this stage almost pure ethylene glycol monoethyl ether acetate distils over, and this is continued until the distillation-residue is 7 weight per cent of the total original charge.  To this residue are then added equimolecular quantities of glycol ether and acetic acid, together with fraction B from the first batch, and an amount of catalyst equal to about one-half that added to the first batch.  The distillation steps are then repeated; and third, fourth and fifth batches are operated in a similar manner.  The process may be used for preparing esters using various alcohols and acids.  Alcohols mentioned are: methyl, ethyl, crotyl, benzyl, cinnamyl, a -phenylallyl, isopropyl, also methyl vinyl carbinol, phenyl methyl carbinol, trimethyl carbinol, ethenyl methyl ethyl carbinol, phenyl methyl ethyl carbinol, phenyl methyl ethenyl carbinol, glycol, diethyleneglycol, triethyleneglycol, a -ethyl glycerol, a -phenylglycerol, 2-methyl-2-methylol propanediol-1,3, cyclohexanol, and the monoethers of ethylene and diethylene glycol.  Acids mentioned are: acetic, crotonic, benzoic, cinnamic, succinic, m-carboxycinnamic, and tricarballylic.  Specification 732,784 is referred to.